The purpooe of this project has been to study, by biochemical and immunochemical techniques, the biosynthesis of a normal acute phase protein SAA (serum amyloid A) which has been identified by its crossreaction with antibodies raised to the amyloid A fibril protein AA. The efforts of this past year have focused on the molecular events by which antigenic and inflammatory agents induce the acute phase SAA response. In the course of carrying out this work, it was necessary to develop a sensitive method for detection of antibodies to AA proteins in the serum of rabbits immunized with crude denatured amyloid A fibrils. Also, the effect of aging on SAA concentration was investigated, by radioimmunoassary analysis of approximately 400 normal healthy individuals ranging in age from 21 to 100. No age related increase in SAA concentration was found.